1. Field of the invention
This invention relates in general to metal seals for sealing between a casing and a wellhead housing, and in particular to a seal that utilizes the weight of the casing to deflect the seal.
2. Description of the Prior Art
In oil and gas wells, casing will be set in the well. A tubular wellhead housing locates at the surface. A casing seal seals the annular space between the upper end of the casing and the wellhead housing. Slips or casing hangers suspend the casing in the wellhead housing.
There are many types of seals and suspension assemblies. Many systems employ elastomeric seals. In the past few years, metal-to-metal seals have become feasible. These types of seals will not deteriorate under long term usage.
Generally, a special seat must be machined in the housing to receive a metal seal. Machining a seat within a housing is complex. Also, a machined seat in a housing may be damaged, making repair difficult. Also, a metal seal normally requires a running tool to deflect the seal into tight sealing engagement. Running tools are normally hydraulically actuated and expensive.